Here's how to instantly figure out when your air quality is getting dangerously bad

A Fitbit can tell you if you're getting enough steps during the day. But it can't warn you when the smog outside is so heavy that those steps might do more harm than good.

The Tzoa tracker, a small wearable device that can be attached to clothing and bags, wants to be the personal health you never knew you needed, giving up-to-the-minute data on air quality, light and UV ray exposure, humidity, and atmospheric pressure.

Kevin Hart, the co-founder and CEO of Tzoa, first came up with the idea while working at a hazardous waste site. His employer gave him a respirator, but Hart had no idea what he was being exposed to.

Creating an air quality tracker that can evaluate pollution both indoors and outdoors was his way of tackling the problem and empowering those around him.

Here's how the $100 tracker calculates air quality: the device contains a small fan that brings in air particles, which then pass through a laser beam that measures the number of particles contained within. It can distinguish between PM2.5 particles, which are small and especially harmful to the lungs, and PM10 particles, like mold and pollen, that trigger allergies.

The Tzoa tracker. Tzoa

An accompanying app tells users whether the air around them is dirty or clean, using personal data as well as crowdsourced information from the Tzoa community.

This isn't the only air quality tracker out there, but Hart believes that Tzoa is unique because of the relevant data it provides. "Other indoor air quality devices exist, and they do a good job of taking VOCs, CO2, carbon monoxide, and air quality metrics, but we're doing a bigger picture," he says. "We're saying, 'Here's an indoor environmental monitor that has the most important air quality metric: particulate matter.'"

Sometimes, too much information is a bad thing — there's only so much you can do if the air is thick with air pollution and you have to go outside anyway, or if your rented apartment contains dangerous amounts of particles.

But if you do have the option of taking the subway instead of walking to work, or fixing a nagging mold problem at the house, Tzoa might be worth a look.